Free Electron Laser Demonstrated at
Brookhaven Lab

The First Step in Developing a Leading-Edge
Research Tool That May Open Up New Fields of Science

UPTON, NY - Researchers from two U.S.
Department of Energy laboratories - Brookhaven National Laboratory
and Argonne National Laboratory - have taken an important first
step in creating a very powerful new tool to generate extremely
intense, coherent pulses of light. Called the high gain harmonic
generation free electron laser (HGHG FEL), this leading-edge technology's
unique capabilities will open up new research opportunities in
chemistry, biology and materials science. The work is reported
in the August 11 edition of the journal Science.

Light is one of the most important investigative
tools for science. The Brookhaven/Argonne team is developing a
means to combine the advantages of two very important light tools:
lasers and accelerators.

Physicist Li Hua Yu, the principal investigator
from Brookhaven on the project, explained, "The HGHG FEL
offers the possibility of combining the intensity and coherence
of a laser with the broad spectrum of light available in a synchrotron,
a type of accelerator. The invention of the laser provided a revolutionary
source of coherent light that created many new fields of scientific
research. The development of the HGHG FEL may extend the reach
of lasers to much shorter wavelengths, thus opening new research
opportunities."

In a proof-of-principle experiment at
Brookhaven's Accelerator Test Facility, the researchers verified
the theoretical foundation of the HGHG FEL operating in the infrared
region of the light spectrum. To extend its usefulness in a wide
range of scientific investigations, work is now focused on refining
the technique to produce pulses of shorter wavelength light in
the deep ultraviolet spectral region, with the ultimate goal of
extending the approach to generate coherent, high-intensity pulses
of X-rays.

There is great interest around the world
in producing coherent X-rays using FEL techniques. The Brookhaven/Argonne
team is unique in investigating the HGHG approach, which will
produce much sharper, short bursts of coherent emissions.

An HGHG FEL would be a complementary
research tool to Brookhaven's National Synchrotron Light Source
(NSLS), a facility used by approximately 2,500 researchers from
around the world each year for a wide range of experiments. The
NSLS generates high-intensity light - from infrared to ultraviolet
and X-rays - for investigating materials as diverse as catalysts
used in refining petroleum, proteins important in drug design,
microcircuits in computers, and moon rocks.

Both the FEL and the NSLS are based
on accelerator technology, but the light pulses produced by a
synchrotron are non-coherent, which means the electrons that emit
the light are unorganized, like musicians playing discordantly
while warming up before a concert. On the other hand, like musicians
playing together in a symphony following a conductor's lead, the
HGHG FEL emits coherent light, which makes the light more useful
for experiments. This coherent emission process facilitates the
production of shorter and more intense pulses of light than can
be provided by a synchrotron. These intense mini-pulses of light
allow researchers to follow a time-dependent process, such as
a chemical reaction as it occurs in a tiny fraction of a second.

The success of the current HGHG FEL
investigation provides a promising roadmap towards using the technique
with shorter wavelengths of light, which will open up ever wider
ranges of experiments. A deep ultraviolet FEL capable of vacuum
ultraviolet operation is now being assembled at Brookhaven. The
proof-of-principle experiments in the ultraviolet range are expected
to take place within two years, and, within the decade, the goal
is to operate a HGHG FEL in the X-ray range.

The U.S. Department of Energy's Brookhaven
National Laboratory creates and operates major facilities available
to university, industrial and government personnel for basic and
applied research in the physical, biomedical and environmental
sciences, and in selected energy technologies. The Laboratory
is operated by Brookhaven Science Associates, a not-for-profit
research management company, under contract with the U.S. Department
of Energy.